Conductive belt and electrophotographic apparatus

ABSTRACT

Concerned with a cylindrical conductive belt for electrophotography which has made permanent curl less occur. The conductive belt has a continuous phase containing a thermoplastic polyester resin and discontinuous phases each containing any one or both selected from a polyether-ester amide and a polyether amide, and the discontinuous phases are present in such way as to extend in the peripheral direction of the belt; the belt having a crystallinity that is lower on the outer-peripheral surface side than on the inner-peripheral surface side.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/JP2011/000890, filed Feb. 17, 2011, which claims the benefit ofJapanese Patent Application No. 2010-042730, filed Feb. 26, 2010.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a cylindrical conductive belt forelectrophotography, used for intermediate transfer belts or the like ofelectrophotographic apparatus, and also relates to anelectrophotographic apparatus.

2. Description of the Related Art

Japanese Patent Application Laid-open No. 2008-89961 discloses aconductive endless belt used for an intermediate transfer belt of anelectrophotographic image forming apparatus in which belt apolyether-ester amide is added as a high-molecular ion-conducting agentto a polyester type elastomer and/or a thermoplastic polyester resin.When compared with a case of making conductive by using as a conductingagent an electron-conductive conducting agent such as carbon black, sucha belt may gently change in conductivity against the amount of theconducting agent to be added, and its electrical resistance can becontrolled with ease.

Here, the polyester type elastomer or thermoplastic polyester resin andthe polyether-ester amide or polyether amide are fundamentallyincompatible with each other. Hence, the conductive endless beltdisclosed in Japanese Patent Application Laid-open No. 2008-89961 takesa structure having a continuous phase constituted of a polyester typethermoplastic elastomer and discontinuous phases each constituted of apolyether-ester amide copolymer. This accords with what is disclosed inJapanese Patent Application Laid-open No. 2008-274286 and JapanesePatent Application Laid-open No. 2005-164674.

SUMMARY OF THE INVENTION

The present inventors have gone through studies on a cylindricalconductive belt which has a continuous phase containing a crystallinethermoplastic polyester resin and discontinuous phases each containing apolyether-ester amide or polyether amide serving as a conducting agentand in which the discontinuous phases are present in such way as toextend in the peripheral direction of the belt.

Here, the cylindrical conductive belt for electrophotography commonlyhas a problem as stated below. That is, the cylindrical conductive beltfor electrophotography is placed in an electrophotographic apparatus insuch a state that it is stretched over a plurality of rollers at aconstant tension. Hence, where the conductive belt stands continuouslyat rest over a long period of time, it has come about that a curl noteasily revertible to normal (hereinafter called “permanent curl”) occursat the part where the belt comes into contact with any roller to havethe largest curvature. Such a portion of the belt for electrophotographyat which the permanent curl has occurred is kept deformed because ofthat permanent curl even when that portion has moved to a position apartfrom the roller. Hence, toner images may insufficiently be transferredto such a deformed portion from an electrophotographic member to causelines or the like in electrophotographic images.

The present inventors have made studies on the mechanism by which thepermanent curl occurs on the above cylindrical conductive belt which hasa continuous phase containing a crystalline thermoplastic polyesterresin and discontinuous phases each containing a polyether-ester amideand in which the discontinuous phases are present in such way as toextend in the peripheral direction of the belt. As the result, they havenewly found that the permanent curl occurring in this conductive belt isparticularly caused by such make-up itself.

Accordingly, the present invention is directed to providing acylindrical conductive belt for electrophotography which is made up asdescribed above, also has superior mechanical strength, and can noteasily cause the permanent curl. Further, the present invention isdirected to providing an electrophotographic apparatus that can stablyform high-grade electrophotographic images.

According to one aspect of the present invention, there is provided acylindrical conductive belt for electrophotography comprising acontinuous phase which comprises a thermoplastic polyester resin, anddiscontinuous phases each of which comprises any one or both selectedfrom a polyether-ester amide and a polyether amide, and thediscontinuous phases are present in such way as to extend in theperipheral direction of the belt; wherein a crystallinity of anouter-peripheral surface side of said cylindrical conductive belt islower than that of an inner-peripheral surface side of said cylindricalconductive belt.

According to another aspect of the present invention, there is providedan electrophotographic apparatus comprising the above conductive belt asan intermediate transfer belt.

According to the present invention, a cylindrical conductive belt forelectrophotography can be obtained which can not easily cause thepermanent curl and has superior mechanical strength. According to thepresent invention, an electrophotographic apparatus can also be obtainedwhich can stably form high-grade electrophotographic images.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an illustration of the conductive belt according to thepresent invention.

FIG. 1B is an illustration of the conductive belt according to thepresent invention.

FIG. 2 is an illustration of the mechanism by which the permanent curloccurs.

FIG. 3 is an illustration of the electrophotographic apparatus accordingto the present invention.

FIG. 4 is a schematic view of a stretch blow molding machine used inproducing the conductive belt according to the present invention.

DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the present invention will now be described indetail in accordance with the accompanying drawings.

The present inventors have analyzed as stated below the mechanism bywhich the permanent curl occurs on the cylindrical conductive belt whichhas a continuous phase containing a crystalline thermoplastic polyesterresin and discontinuous phases each containing a polyether-ester amideand in which the discontinuous phases are present in such way as toextend in the peripheral direction of the belt.

First, they have grasped that the permanent curl is a state in which theconductive belt has lost the force of being restored to an originalshape like that of rubber, at its part where it stands wound around anyroller over which it is stretched, and its shape of being kept woundaround the roller is somewhat maintained.

Here, FIG. 1A is a perspective view of a cylindrical conductive beltwhich has a continuous phase containing a thermoplastic polyester resinand discontinuous phases each containing any one or both selected from apolyether-ester amide and a polyether amide and in which thediscontinuous phases are present in such way as to extend in theperipheral direction of the belt. FIG. 1B is a partial enlarged view ofa cross section in the peripheral direction of the belt shown in FIG.1A. In FIGS. 1A and 1B, reference numeral 101 denotes the continuousphase containing a thermoplastic polyester resin (hereinafter alsosimply “PE”); and 103, the discontinuous phases each containing any oneor both selected from a polyether-ester amide and a polyether amide.Then, the discontinuous phases 103 are present in such way as to extendin the peripheral direction of the conductive belt.

The present inventors have made observation on a cross section in theperipheral direction of the belt at the part where the permanent curlhas occurred because the conductive belt having the afore-mentionedconstruction, has been stretched over two rolls and left to stand in astationary state over a long period of time. As the result, as shown inFIG. 2, there have been found to be micro-crevices 102 at the interfacesbetween a continuous phase and discontinuous phases present on theouter-peripheral surface side of the conductive belt. Thesemicro-crevices are considered to have been caused by the difference inbehavior between the continuous phase and the discontinuous phases, whena tensile force has been acted on the outer-peripheral surface side ofthe conductive belt. Then, they have presumed that, such micro-crevicescome to weaken physical binding between the continuous phase and thediscontinuous phases. As a result of that, the conductive belt'srestoring force to its original shape has weakened, and therefore, thepermanent curl has been caused.

Accordingly, the present inventors have gone through studies so as toprevent the micro-crevices at the interfaces between the continuousphase and the discontinuous phases, which micro-crevices are consideredto be the cause of the permanent curl, from occurring. As the result, itis discovered that the construction, in the thickness direction of theconductive belt, having higher crystallinity of the inner-peripheralsurface side, to which compression force is applied, than that of theouter-peripheral surface side, to which tensile force is applied, cansuppress the occurrence of the micro-crevices at the interfaces, and italso contributes to the reduction of the permanent curl.

The reason why the relative relationship of the crystallinity betweenthe inner-peripheral surface side and outer-peripheral surface side asstated above reduces the occurrence of permanent curl is unclear, andthey presume it as stated below.

When the cylindrical conductive belt stands stretched over a pluralityof rollers, tensile force is applied to its outer-peripheral surfaceside at the part where the conductive belt comes into contact with anyroller and compression force is applied to the inner-peripheral surfaceside thereof, as having been stated above. On this occasion, bydecreasing the crystallinity of the outer-peripheral surface side of thebelt relative to that of the inner-peripheral surface side of the belt,and allowing the outer-peripheral surface side to be stretchable by theaction of the tensile force acting on the outer-peripheral surface side,stress concentration to the interfaces between the continuous phase andthe discontinuous phases is relieved. Therefore, the occurrence of themicro-crevices at the interfaces between the continuous phase and thediscontinuous phases is believed to be suppressed.

On the other hand, at the inner-peripheral surface side, wherecompressive force is to act, the compressive force acts when the beltcomes into contact with any roller, and the belt is released from thecompressive force when the contact with the roller comes free. On thisoccasion, by increasing the crystallinity of the inner-peripheralsurface side of the belt relative to that of the outer-peripheralsurface side, and making more dense construction, restoration to theoriginal shape after the inner-peripheral surface side of the conductivebelt is released from the compressive force can be more strengthened.

As the result, as the whole conductive belt, the shape of the placewhere prolonged contact with the roller comes free can easily berestored to the original shape, and therefore, the occurrence of thepermanent curl is considered to be suppressed

Now, the construction of the cylindrical conductive belt forelectrophotography according to the present invention is described. Theconductive belt 100 according to the present invention has, at its crosssection in the peripheral direction and as shown in FIG. 1B, thecontinuous phase 101 containing a thermoplastic polyester resin and thediscontinuous phases 103 each containing any one or both selected from apolyether-ester amide and a polyether amide. Also, the discontinuousphases 103 are present in such way as to extend in the peripheraldirection of the belt. Then, the conductive belt has a crystallinitythat is lower on the outer-peripheral surface side than on theinner-peripheral surface side.

First, the discontinuous phases 103 each containing a polyether-esteramide and/or a polyether amide are made present in such way as to extendin the peripheral direction of the belt. This can make relatively shortthe distance between the discontinuous phases present in plurality. Asthe result, leak currents tend to flow across the discontinuous phasespresent in plurality, so that the conductive belt can be improved in itsconductivity, as having such technical significance.

The technical significance in that the conductive belt has acrystallinity that is relatively lower on the outer-peripheral surfaceside than on the inner-peripheral surface side is as stated above.Specific crystallinity on the outer-peripheral surface side and on theinner-peripheral surface side each may appropriately be controlled inaccordance with the diameters of rollers over which the conductive beltis to be stretched, and its tension. A specific method of controllingthe crystallinity is detailed later as a method for producing theconductive belt according to the present invention.

Materials for the conductive belt according to the present invention aredescribed next.

Thermoplastic Polyester Resin:

The thermoplastic polyester resin (hereinafter simply “PE”) thatconstitutes the continuous phase 101 may be obtained by polycondensationof a dicarboxylic acid component with a dihydroxyl component,polycondensation of a hydroxycarboxylic acid component or a lactonecomponent, or polycondensation making use of any of these components inplurality. The PE may be a homo-polyester or may also be a co-polyester.

Specific examples of the dicarboxylic acid component are shown below.

Aromatic dicarboxylic acids having 8 or more to 16 or less carbon atomsin the molecule, such as terephthalic acid, isophthalic acid, phthalicacid, and naphthalene dicarboxylic acid (such as 2,6-naphthalenedicarboxylic acid), diphenyl dicarboxylic acid, diphenyl etherdicarboxylic acid, diphenylmethane dicarboxylic acid, and diphenylethanedicarboxylic acid;

alicyclic dicarboxylic acids including cycloalkane dicarboxylic acidshaving 4 to 10 carbon atoms in the molecule, such as cyclohexanedicarboxylic acid; and

aliphatic dicarboxylic acids including aliphatic dicarboxylic acidshaving 4 to 12 carbon atoms in the molecule, such as succinic acid,adipic acid, azelaic acid and sebacic acid.

Derivatives of the above dicarboxylic acids may also be used. Statedspecifically, they may be exemplified by derivatives capable of formingesters, e.g., lower alkyl esters such as dimethyl ester, acidanhydrides, and acid halides such as acid chloride. Any of thesedicarboxylic acid components may be used alone or in combination of twoor more types. Preferred dicarboxylic acid components are the aromaticdicarboxylic acids, from the viewpoint of crystallizability and heatresistance, and much preferred are terephthalic acid, isophthalic acidand naphthalene dicarboxylic acid.

Examples of the dihydroxyl component are shown below.

Alkylene diols having 2 to 10 carbon atoms in the molecule, such asethylene glycol, propylene glycol, 1,3-butane diol, 1,4-butane diol,neopentyl glycol, and hexane diol;

alicyclic diols having 4 to 12 carbon atoms in the molecule, such ascyclohexane diol and cyclohexane dimethanol;

aromatic diols having 6 to 20 carbon atoms in the molecule, such ashydroquinone, resorcin, dihydroxybiphenyl, naphthalene diol,dihydroxydiphenyl ether, and 2,2-bis(4-droxyphenyl)propane (bisphenolA);

alkylene oxide addition products of the above aromatic diols, e.g.,alkylene oxide addition products having 2 to 4 carbon atoms, ofbisphenol A; and

polyoxyalkylene glycols such as diethylene glycol, polyoxyethyleneglycol, polyoxypropylene glycol, and polytetramethylene ether glycol.

These dihydroxyl components may be derivatives capable of formingesters, as exemplified by alkyl group, alkoxyl group or halogensubstituted products. Any of these dihydroxyl components may be usedalone or in combination of two or more types. Of these dihydroxylcomponents, it is preferable from the viewpoint of crystallizability,heat resistance and so forth to use alkylene diols (in particular,alkylene diols having 2 to 4 carbon atoms) and alicyclic diols.

The hydroxycarboxylic acid component may be exemplified byhydroxycarboxylic acids such as hydroxybenzoic acid, hydroxynaphthoicacid, diphenylene hydroxybenzoic acid and 2-hydroxypropionic acid, andderivatives of these hydroxybenzoic acids. Any of these hydroxybenzoicacids may be used alone or in combination of two or more types.

The lactone component may include C3 to C12 lactones such aspropiolactone, butyrolactone, valerolactone and caprolactone (e.g.,ε-caprolactone). Any of these lactones may also be used alone or incombination of two or more types.

Further, a polyfunctional monomer may also be used in combination aslong as the crystallizability and heat resistance are maintained. Thepolyfunctional monomer may include as examples thereof polybasiccarboxylic acids such as trimellitic acid, trimesic acid andpyromellitic acid, and polyhydric alcohols such as glycerol, trimethylolpropane, trimethylol ethane and pentaerythritol. A polyester may also beused which has a branched or cross-linked structure, formed by the useof such a polyfunctional monomer.

The PE may be produced by polycondensation making use of the abovecomponent (the dicarboxylic acid component, the dihydroxyl component,the hydroxycarboxylic acid component or the lactone component, or aplurality of any of these components). Then, from the viewpoint ofcrystallizability, heat resistance and so forth, the PE is at least oneselected from a polyalkylene terephthalate, a polyalkylene naphthalateand a copolymer of a polyalkylene terephthalate and a polyalkyleneisophthalate. The copolymer may include, e.g., a block copolymer and arandom copolymer. The alkylene in the polyalkylene terephthalate,polyalkylene naphthalate and polyalkylene isophthalate each maypreferably have 2 or more to 16 or less carbon atoms from the viewpointof crystallizability and heat resistance. The PE may further preferablybe at least one selected from polyethylene terephthalate, a copolymer ofpolyethylene terephthalate and polyethylene isophthalate, andpolyethylene naphthalate. It may also be a blend or alloy of two or moretypes as long as it is the thermoplastic polyester resin.

The polyethylene naphthalate may include as specific examples thereofTN-8050SC (trade name; available from Teijin Chemicals Ltd.) andTN-8065S (trade name; available from Teijin Chemicals Ltd.), which arecommercially available. The polyethylene terephthalate may includeTR-8550 (trade name; available from Teijin Chemicals Ltd.), which iscommercially available, and the copolymer of polyethylene terephthalateand polyethylene isophthalate may include PIFG30 (trade name; availablefrom Bell Polyester Products, Inc.), which is commercially available.

The PE may preferably have an intrinsic viscosity of 1.4 dl/g or less,much preferably from 0.3 dl/g or more to 1.2 dl/g or less, and furtherpreferably from 0.4 dl/g or more to 1.1 dl/g or less. As long as it hasan intrinsic viscosity of 1.4 dl/g or less, its fluidity can be keptfrom lowering at the time of molding. As long as it has an intrinsicviscosity of 0.3 dl/g or more, the conductive belt according to thepresent invention can be much more improved in its strength anddurability. Here, the intrinsic viscosity of the PE is the value foundby measurement made using o-chlorophenol as a diluting solvent for thethermoplastic polyester resin and setting the concentration of theresultant o-chlorophenol solution to 0.5% by mass and its temperature at2° C.

The PE may preferably be in an amount of 50% by mass or more,particularly preferably 60% by mass or more, and further preferably 70%by mass or more, based on the total mass of the PE and thepolyether-ester amide (PEEA) and polyether amide (PEA) detailed later.As long as it is in an amount of 50% by mass or more, the belt forelectrophotography can more effectively be kept from lowering indurability.

Polyether-Ester Amide (PEEA) & Polyether Amide (PEA):

The PEEA may include, e.g., compounds composed chiefly of a copolymerconsisting of a polyamide block unit such as nylon 6, nylon 66, nylon 11or nylon 12 and a polyether ester unit. For example, it may include acopolymer derived from a) a lactam (e.g., caprolactam or lauryl lactam)or a salt of aminocarboxylic acid, b) polyethylene glycol and c) adicarboxylic acid. The dicarboxylic acid may include as specificexamples thereof terephthalic acid, isophthalic acid, adipic acid,azelaic acid, sebacic acid, undecane diacid and dodecane diacid.

The PEEA may be produced by a known polymerization process such as meltpolymerization. Of course, it is by no means limited to the above, andit may also be a blend or alloy of two or more types. Commerciallyavailable PEEAs may also be used (trade name: IRGASTAT P20; availablefrom Ciba Specialty Chemicals), (trade name: TPAE H151; available fromFuji Kasei Co., Ltd.) and (trade name: PELLESTAT NC6321; available fromSanyo Chemical Industries, Ltd.).

The PEA may include, e.g., compounds composed chiefly of a copolymerconsisting of a polyamide block unit such as nylon 6, nylon 66, nylon 11or nylon 12, a polyether diamine unit and a dicarboxylic acid unit. ThePEA may include as a specific example thereof a copolymer derived froma) a lactam (e.g., caprolactam or lauryl lactam) or a salt ofaminocarboxylic acid, b) polytetramethylene diamine and c) adicarboxylic acid. As the dicarboxylic acid, the same as the above maybe used.

The PEA may be produced by a known polymerization process such as meltpolymerization. Of course, it is by no means limited to the above, andit may also be a blend of two or more types of the polyether amide, oran alloy of these. Commercially available PEA may also be used (tradename: PEBAX 5533; available from ARKEMA Co.).

Amount

The PEEA and PEA may preferably be in a total amount of from 3% by massor more to 30% by mass or less, and particularly preferably from 5% bymass or more to 20% by mass or less, based on the total mass of the PE,PEEA and PEA. The PEEA and PEA function as conducting agents.Accordingly, inasmuch as they are in a total amount of 3% by mass ormore, a thermoplastic resin composition used for producing the belt ofthe present invention and furthermore the belt for electrophotographyproduced can be made to have an appropriately low electrical resistance.Also, inasmuch as they are in a total amount of 30% by mass or less, thethermoplastic resin composition can well be kept from having a lowviscosity because of the decomposition of resins, and, as a result ofthis, the belt for electrophotography formed can further be improved indurability.

Additives:

Any one of both of the discontinuous phases and the continuous phase maybe incorporated with any other component(s), e.g., an insulating filler,as long as the effect of the present invention is not damaged. Specificexamples of the insulating filler are given below: Zinc oxide, bariumsulfate, calcium sulfate, barium titanate, potassium titanate, strontiumtitanate, titanium oxide, magnesium oxide, magnesium hydroxide andaluminum hydroxide.

Production Method:

The conductive belt according to the present invention has threecharacteristic features in make-up. The first feature is that it has thecontinuous phase containing PE and the discontinuous phases eachcontaining any one or both selected from PEEA and PEA, the secondfeature is that the discontinuous phases are present in such way as toextend in the peripheral direction of the belt, and the third feature isthat the belt has a crystallinity that is lower on the outer-peripheralsurface side than on the inner-peripheral surface side.

Then, for the achievement of the first-feature make-up, it is necessaryto control how the thermoplastic resin composition used for producingthe conductive belt be formulated. More specifically, where the massratio of the mass of the PE to the total mass of the thermoplastic resincomposition used for producing the conductive belt is represented by Aand the mass ratio of the total mass of the PEEA and PEA to the totalmass of the thermoplastic resin composition used for producing theconductive belt is represented by B, it is necessary to be A>B. It maymuch preferably be A/B>2.

For the achievement of the second-feature make-up, a method is employedin which a test tube-shaped preform (a preform in the shape of a testtube) composed of the thermoplastic resin composition specificallyformulated as above is made by biaxial orientation molding to produce abelt in a seamless form. Such a method itself is known in the art asdisclosed in Japanese Patent Applications Laid-open No. 2006-76154 andNo. 2001-18284. A specific method for obtaining the conductive belt in aseamless form by biaxial orientation molding is described below.

First, the test tube-shaped preform composed of the thermoplastic resincomposition is prepared. Next, the preform, having been heated, isfitted to the interior of a seamless belt forming mold. Thereafter, thetest tube-shaped preform is stretched from its inside by using astretching rod, to orient the preform in its axial direction and also byblowing a gas into the preform to orient the preform in its diametricaldirection to obtain a bottle-shaped molded product. Then, thebottle-shaped molded product is cut at the middle thereof to obtain aseamless belt.

The employment of such a biaxial orientation molding process enables aconductive belt in a seamless form to be obtained in which thediscontinuous phases have been oriented in the peripheral direction andextend in the peripheral direction. Here, the discontinuous phases mayhave an aspect ratio of approximately from 10 to 30, and particularlyfrom 15 to 25, as average value. Here, the aspect ratio refers to theproportion of the length (l) in the peripheral direction with respect tothe thickness maximum value (t) of discontinuous phases appearing on across section when the cylindrical conductive belt is cut in a circle.

Finally, the third-feature make-up can be achieved by controlling thecrystal state of the preform composed of the thermoplastic resincomposition and having the shape of a test tube and controlling thesurface temperatures of the inner wall and outer wall of the preformwhen the preform is biaxially oriented.

The test tube-shaped preform composed of the thermoplastic resincomposition is firstly required to have a state that is amorphous enoughto be feasible for the biaxial orientation, detailed later. Such apreform may be obtained by controlling the mold temperature when thethermoplastic resin composition is molded by injecting it into apreform-shaped mold. Stated specifically, the thermoplastic resincomposition is quenched in the mold in the state the mold temperature isset at a temperature sufficiently lower than the melting point of thethermoplastic resin composition. For example, a thermoplastic resincomposition shown in Table 1 below has a melting point of 260° C. Such athermoplastic resin composition is molded by injecting it into a moldtemperature-controlled at a mold temperature of from 30° C. to 40° C.,whereby a preform can be obtained which is amorphous enough to befeasible for the biaxial orientation.

TABLE 1 PE Polyethylene naphthalate 80 parts (trade name: TN-8050SC;available by mass from Teijin Chemicals Ltd.); Tm: 260° C.; Tg: 120° C.;intrinsic viscosity: 0.50 dl/g (temperature 25° C., 0.5% by masssolution of o-chlorophenol) PEEA (trade name: IRGASTAT P20; 18 partsavailable from Ciba Specialty by mass Chemicals) Tm: 180° C.; Tg: −50°C. Additive Potassium perfluorobutane sulfonate  2 parts (trade name:KFBS; available from by mass Mitsubishi Materials Corporation)

Next, this amorphous preform is heated and stretched in the mold toeffect biaxial orientation, where the inner-wall heating temperature andouter-wall heating temperature of the preform when the bottle-shapedmolded product is formed are controlled within the temperature range offrom not lower than the glass transition temperature of thethermoplastic resin composition to not higher than the melting point ofthe same. Stated specifically, the preform is so heated that itsinner-wall surface temperature may come to be ±5° C. of crystallizationtemperature of the preform. Meanwhile, about the outer wall, the preformis so heated that its outer-wall surface temperature may come to be notlower than the glass transition temperature of the preform and nothigher than −10° C. of crystallization temperature of the same. Thepreform composed of the thermoplastic resin composition shown in Table 1above has a crystallization temperature of 170° C. Accordingly, thepreform may preferably be so heated that its inner-wall surfacetemperature may come to be within the range of from 165° C. to 175° C.and its outer-wall surface temperature may come to be within the rangeof from 100° C. to 160° C. Then, the respective inner-wall surfacetemperature and outer-wall surface temperature may be controlled withinthe above ranges, and this enables control of the crystallinity on theinner-peripheral surface side and outer-peripheral surface side each ofthe conductive belt.

Then, for the preform having been heated in such a state, the stretchingrod is used to orient the preform in its axial direction and alsoblowing a gas into the preform to orient the preform in its diametricaldirection to obtain the bottle-shaped molded product. Here, thetemperature of the gas to be blown into the preform may preferably bekept so controlled that the inner wall of the preform may not deviatefrom the above temperature range during the step of orienting thepreform. Incidentally, as to the temperature of the mold with which thesurface of the bottle-shaped molded product obtained by the biaxialorientation of the preform comes into contact, any effect it may have onthe crystallinity of the outer wall of the bottle-shaped molded productis negligible.

The bottle-shaped molded product thus obtained is cut at the middlethereof in a stated width to obtain the cylindrical conductive beltaccording to the present invention.

The conductive belt for electrophotography may commonly have a thicknessof from 10 μm or more to 500 μm or less, and particularly from 30 μm ormore to 150 μm or less. The conductive belt may also have volumeresistivity controlled appropriately by controlling the amount of the PEand PEEA or PEA depending on what the conductive belt is used for.Stated specifically, where the conductive belt is used as anintermediate transfer belt, it may have a specific volume resistivity ofapproximately from 1×10² Ω·cm or more to 1×10¹⁴ Ω·cm or less.

Electrophotographic Apparatus:

The conductive belt according to the present invention is described.FIG. 3 is a sectional view of a full-color electrophotographicapparatus. In what is shown in FIG. 3, the cylindrical conductive beltaccording to the present invention is used as an intermediate transferbelt 5.

An electrophotographic photosensitive member 1 is a rotary drum-typephotosensitive member (hereinafter called “photosensitive drum”) usedrepeatedly as a first image bearing member, which is rotatingly drivenat a stated peripheral speed (process speed) in the direction of anarrow. The photosensitive drum 1 is, in the course of its rotation,uniformly electrostatically charged to stated polarity and potential bymeans of a primary charging assembly 2. Then, it is imagewise exposed toexposure light 3 emitted from an exposure means. Thus, an electrostaticlatent image is formed which corresponds to a first color componentimage (e.g., a yellow color component image) of the intended colorimage. Here, as the exposure means, it may include a color-originalimage color-separating and image-forming optical system, and a scanningexposure system operated by a laser scanner that outputs laser beamsmodulated in accordance with time-sequential electrical digital pixelsignals of image information.

Next, the electrostatic latent image is developed with a first-color,yellow toner Y, by means of a first developing assembly (yellow colordeveloping assembly 41). At this stage, second to fourth developingassemblies (a magenta color developing assembly 42, a cyan colordeveloping assembly 43 and a black color developing assembly 44) eachstand unoperated and do not act on the photosensitive drum 1, and thefirst-color yellow toner image is not affected by the second to fourthdeveloping assemblies.

The intermediate transfer belt 5 is rotatingly driven in the directionof an arrow at the same peripheral speed as the photosensitive drum 1.The yellow toner image formed and held on the photosensitive drum 1passes through a nip zone formed between the photosensitive drum 1 andthe intermediate transfer belt 5, in the course of which it istransferred to the peripheral surface of the intermediate transfer belt5 (primary transfer) by the aid of an electric field formed by a primarytransfer bias applied to the intermediate transfer belt 5 through anopposing roller 6.

The photosensitive drum 1 surface from which the first-color yellowtoner image has been transferred to the intermediate transfer belt 5 iscleaned by a cleaning assembly 13. Subsequently, the second-colormagenta toner image, the third-color magenta toner image and thefourth-color black toner image are sequentially likewise transferredsuperimposingly onto the intermediate transfer belt 5. Thus, asynthesized full-color toner image is formed which corresponds to theintended color image. A secondary transfer roller 7 is provided in sucha way that it is axially supported in parallel to a drive roller 8 andstands separable from the bottom surface of the intermediate transferbelt 5.

In the step of primary transfer of the first- to third-color tonerimages from the photosensitive drum 1 to the intermediate transfer belt5, the secondary transfer roller 7 may be separated from theintermediate transfer belt 5.

The synthesized full-color toner image transferred onto the intermediatetransfer belt 5 is secondarily transferred to a second image bearingmember, transfer material P, in the following way: First, the secondarytransfer roller 7 is brought into contact with the intermediate transferbelt 5 and simultaneously the transfer material P is fed at a statedtiming from a paper feed roller 11 through a transfer material guide 10until it reaches a contact nip formed between the intermediate transferbelt 5 and the secondary transfer roller 7. Then, a secondary transferbias is applied to the secondary transfer roller 7 from a power source31. By the aid of this secondary transfer bias, the synthesizedfull-color toner image is transferred (secondary transfer) from theintermediate transfer belt 5 to the second image bearing member,transfer material P. The transfer material P to which the synthesizedfull-color toner image has been transferred is guided into a fixingassembly 15, where this full-color toner image is heat-fixed.

After the synthesized full-color toner image has been transferred to thetransfer material P, an intermediate transfer belt cleaning roller 9 ofa cleaning assembly is brought into contact with the intermediatetransfer belt 5, and a bias with a polarity reverse to that of thephotosensitive drum 1 is applied, whereupon electric charges with apolarity reverse to that of the photosensitive drum 1 are imparted totoners not transferred to the transfer material P and remaining on theintermediate transfer belt 5 (i.e., transfer residual toners). Referencenumeral 33 denotes a power source. The transfer residual toners areelectrostatically transferred to the photosensitive drum 1 at the nipzone between the photosensitive drum 1 and the intermediate transferbelt 5, and the vicinity thereof, thus the intermediate transfer belt 5is cleaned.

EXAMPLES

The present invention is specifically described below by giving Examplesand Comparative Examples, to which Examples, however, the presentinvention is by no means limited. In these Examples and ComparativeExamples, seamless belts for electrophotography were produced as thoseincluded in the conductive belt, and analyses and measurement ofphysical properties as given in Examples and Comparative Examples weremade in the following way.

How to Measure and Evaluate Characteristic Values:

How to measure and evaluate characteristic values of the seamless beltsfor electrophotography which were produced in Examples and ComparativeExamples are as follows:

(1) Volume Resistivity (ρV):

As measuring equipments, an ultra-high resistance meter (trade name:R8340A; manufactured by Advantest Corporation) was used as a resistancemeter, and Sample Box for ultra-high resistance measurement (trade name:TR42; manufactured by Advantest Corporation) as a sample box. The mainelectrode was 25 mm in diameter, and the guard-ring electrode was 41 mmin inner diameter and 49 mm in outer diameter (according to ASTMD257-78).

A sample for measuring the volume resistivity of the seamless belt forelectrophotography was prepared in the following way. First, theseamless belt for electrophotography was cut in a circular form of 56 mmin diameter by means of a punching machine or a sharp knife. Thecircular cut piece obtained was, on its one side, fitted with anelectrode over the whole surface by forming a Pt—Pd deposited film and,on the other side, fitted with a main electrode of 25 mm in diameter anda guard electrode of 38 mm in inner diameter and 50 mm in outer diameterby forming Pt—Pd deposited films. The Pt—Pd deposited films were formedby carrying out vacuum deposition for 2 minutes using a sputteringsystem (trade name: MILD SPUTTER E1030; manufactured by Hitachi Ltd.),at an electric current of 15 mA and at a distance of 15 mm between atarget (Pt—Pd) and the sample (the circular piece of the seamless beltfor electrophotography. The circular piece on which the vacuumdeposition was completed was used as a measuring sample.

The measurement was made in an atmosphere of temperature 23° C. andrelative humidity 52%. The measuring sample was previously kept left inthe like atmosphere for 12 hours or longer. The volume resistivity wasmeasured under a mode of discharge for 10 seconds, charge for 30 secondsand measurement for 30 seconds and at an applied voltage of 100 V. Thevolume resistivity was measured 10 times under this mode, and an averagevalue of the values of this measurement made 10 times was taken as thevolume resistivity of the seamless belt for electrophotography.

(2) Crystallinity:

The belt for electrophotography obtained was cut in a size of 30 mm×30mm, and the crystallinity was measured on the inner-peripheral surfaceside and outer-peripheral surface side of the belt forelectrophotography by using the following instrument and under thefollowing conditions.

-   Instrument: X-ray diffractometer manufactured by Rigaku Corporation,    RINT-2200-   Output: 30 kV-50 mA-   Target: Cu (CuKα)-   Optical system: First pinhole collimator, 1.0 mm in diameter-   Receiving slits (slit made lengthwise: 1°; slit made breadthwise:    1°)-   Condition for measurement: Parallel beam collimation-   Rate of measurement: 10°/minute-   Goniometry range: 2θ=5˜40°    From the integral intensities of peaks at diffraction angles    2θ=5˜40° where diffraction peaks appear for both the amorphous    portion and crystalline portion of the resin, the crystallinity (%)    was calculated according to the following expression (1).

Crystallinity=[integral intensity of crystalline portion (peak at around2θ=26°/integral intensity of portion inclusive of amorphous andcrystalline (2θ=5˜40°)]×100   Expression (1)

(3) Average Aspect Ratio of Discontinuous Phases:

The belt for electrophotography was cut with a microtome or the like ata thickness cross section in the peripheral direction of the belt, andthis cross section was observed on a field emission scanning microscope(FE-SEM) XL30 (trade name; manufactured by FEI Technology Co.). In anislands-in-sea structure (the sea component is the polyester and theisland component is the polyether amide) observed from the crosssection, the aspect ratios of portions corresponding to individualislands within the range of 100 μm×100 μm were calculated by binary-codeprocessing to take an average value thereof.

(4) Height of Permanent Curl:

The conductive belt was fitted as an intermediate transfer belt to anintermediate transfer unit of a laser beam printer LBP-5200(manufactured by CANON INC.), having the apparatus structure as shown inFIG. 3. The intermediate transfer belt of this laser beam printer wasstretched over a drive roller of 18 mm in diameter and a tension rollerof 15 mm in diameter at a stretch-over stress of 6 kgf. This laser beamprinter was left to stand at rest for a month in an environment oftemperature 35° C. and relative humidity 95%.

Next, the conductive belt was rotatingly driven by some level, and thenits part where it was in contact with the drive roller during theleaving at rest was separated from the drive roller, in the state ofwhich it was left to stand at rest for a day in an environment oftemperature 35° C. and relative humidity 95% RH. Thereafter, the heightof a trail of contact of the drive roller at the part of the conductivebelt where the drive roller was in contact therewith during the leavingat rest was measured with a surface profile analyzer (trade name:SE-3500; manufactured by Kosaka Laboratory Ltd.). This height wasdefined as permanent curl height. The larger this height is, the moreany faulty primary transfer of toner images to that part tends to occur.

(5) Image Evaluation:

After the above evaluation (4), in an environment of temperature 23° C.and relative humidity 50% RH, orange solid images were printed on 155g/m² A4-size gloss paper by using yellow and magenta two colors. Theimages obtained were visually observed to ascertain whether or not anylines caused by permanent curl were seen, and evaluation was madeaccording to the following criteria.

-   A: Any line is not seen.-   B: Lines are seen.

Materials of Thermoplastic Resin Compositions used in Examples andComparative Examples:

Materials of thermoplastic resin compositions used in Examples andComparative Examples given later are shown in Tables 2 to 4.

TABLE 2 PE1 Polyethylene naphthalate (trade name: TN-8050SC; availablefrom Teijin Chemicals Ltd.); Tm: 260° C.; intrinsic viscosity: 0.50 dl/g(temperature 25° C., 0.5% by mass solution of o-chlorophenol) PE2Polyethylene terephthalate (trade name: TR-8550; available from TeijinChemicals Ltd.); Tm: 260° C.; intrinsic viscosity: 0.50 dl/g(temperature 25° C., 0.5% by mass solution of o-chlorophenol)

TABLE 3 PEEA Trade name: IRGASTAT P20; available from Ciba SpecialtyChemicals); Tm: 180° C. PEA Trade name: PEBAX 5533; available fromARKEMA Co.; Tm: 170° C.

TABLE 4 Additive Surface-active agent (potassium perfluorobutanesulfonate; available from Mitsubishi Materials Corporation)

Example 1

Using a twin-screw extruder (trade name: TEX30α, manufactured by TheJapan Steel Works, Ltd.), the above materials were hot-melt-kneadedunder formulation shown in Table 5, to prepare a thermoplastic resincomposition. Hot-melt kneading temperature was so controlled as to bewithin the range of from 260° C. or more to 280° C. or less, andhot-melt kneading time was set to about 3 to 5 minutes. Thethermoplastic resin composition obtained was made into pellets, whichwere then dried at a temperature of 140° C. for 6 hours. Next, thepelletized thermoplastic resin composition thus dried was put into aninjection molding machine (trade name: SE180D, manufactured by SumitomoHeavy Industries, Ltd.). Then, cylinder preset temperature was set at295° C., and the pelletized thermoplastic resin composition was moldedby injecting it into a mold temperature-controlled at a temperature of30° C. to prepare a preform. The preform obtained had the shape of atest tube of 20 mm in outer diameter, 18 mm in inner diameter and 150 mmin length. Then, by the following method, it was ascertained that thispreform was one involving an amorphous state.

How to Ascertain Amorphous Property of Preform:

A sample of 1 mm in length and 1 mm in breadth was cut out from thepreform, and this sample was measured with a differential scanningcalorimeter (DSC). The measurement was made under conditions of heatingat from 25° C. to 300° C. at a heating rate of 10° C./minute. Where anyamorphous component remains, a crystallization exothermic peak appearswhich is seen at around 170° C. Then, the exothermic calorie of thecrystallization exothermic peak in this sample was found to be 38 J/g.Meanwhile, the endothermic calorie of the melt endothermic peak seen ataround 260° C. was found to be 62 J/g. From the fact that the exothermiccalorie of the crystallization exothermic peak was ½ or more of theendothermic calorie of the melt endothermic peak, it was ascertainedthat the preform retained its amorphous component sufficiently.

Next, the above preform was biaxially oriented by using a biaxialorientation apparatus shown in FIG. 4. Before biaxial orientation, apreform 104 was placed in a heating unit 107 having a non-contact typeheater (not shown) for heating the outer wall and inner wall of thepreform 104, and, using an outside heater and an inside heater whichwere set at temperatures shown in Table 5, the outer wall and inner wallof the preform were so heated as to have their surface temperaturesshown in Table 5. Then, the preform 104 thus heated was placed inside ablow mold 108 kept at a mold temperature of 110° C., and oriented in itsaxial direction by using a stretching rod 109. At the same time, airtemperature-controlled at a temperature of 23° C. was guided into thepreform through a blow air blowing inlet 110 to orient the preform 104in its diametrical direction. Thus, a bottle-shaped molded product 112was obtained. Then, the bottle-shaped molded product 112 was cut at themiddle thereof to obtain a seamless conductive belt. This conductivebelt was 70 μm in thickness. Results of evaluation of this conductivebelt are shown in Table 6.

Examples 2 to 9

Seamless belt for electrophotography were obtained in the same way as inExample 1 except that the formulation of each thermoplastic resincomposition, the outside heater temperature, the inside heatertemperature, the outer-wall surface temperature and the inner-wallsurface temperature were made or changed as shown in Table 5. Results ofevaluation of these conductive belts are shown in Table 6.

TABLE 5 Example: 1 2 3 4 5 6 7 8 9 Thermoplastic resin composition PE1(parts by mass) 80 80 80 85 90 75 — — 60 PE2 (parts by mass) — — — — — —80 80 — PEEA (parts by mass) 18 18   12 6 25 18 — 38 PEA (parts by mass)— — 18 — — — — 18 — Additive (parts by mass) 2 2 2 3 4 — 2 2 2 Glasstransition temp. (° C.) 100 100 101 101 103 97 75 76 95 Crystallizationtemp. (° C.) 170 170 171 168 166 173 132 134 175 Melting point (° C.)261 261 261 260 261 260 261 261 260 Molding conditions Outside heatertemp. (° C.) 500 600 500 500 500 500 350 350 500 Inside heater temp. (°C.) 700 800 700 700 700 700 500 500 700 Preform outer-wall 150 155 150151 150 150 115 116 151 surface temp. (° C.) Preform inner-wall 165 175165 166 165 165 130 132 164 surface temp. (° C.) Crystallinity (%) ofbelt on 50 45 52 55 55 40 44 45 22 outer peripheral surface sideCrystallinity (%) of belt on 55 53 58 61 60 45 49 48 27 inner peripheralsurface side

In the above, the glass transition temperature, the crystallizationtemperature and the melting point are temperature at a point ofinflection (glass transition temperature) and a peak top temperature(crystallization temperature and melting point) which were each foundusing a differential scanning calorimeter (DSC) by making theirmeasurement at a heating rate of 10° C./minute.

TABLE 6 Example: 1 2 3 4 5 6 7 8 9 Volume resistivity (Ω · cm) 1 × 10¹¹2 × 10¹¹ 9 × 10¹⁰ 1 × 10¹¹ 2 × 10¹² 3 × 10¹¹ 8 × 10¹⁰ 1 × 10¹¹ 5 × 10¹⁰Average aspect ratio of 16 18 17 17 18 15 15 17 25 discontinuous phasesAverage height of 70 60 75 55 60 80 75 80 75 permanent curl Imageevaluation A A A A A A A A A

Comparative Examples 1 to 9

Seamless conductive belts were obtained in the same way as in Example 1except that the formulation of each thermoplastic resin composition, theoutside heater temperature, the inside heater temperature, theouter-wall surface temperature and the inner-wall surface temperaturewere made or changed as shown in Table 7. These conductive belts wereevaluated in the same way as in Example 1. Results of evaluation areshown in Table 8.

TABLE 7 Comparative Example: 1 2 3 4 5 6 7 8 9 Thermoplastic resincomposition PE1 (parts by mass) 80 80 80 90 90 — — — 60 PE2 (parts bymass) — — — — — 80 80 80 — PEEA (parts by mass) 18 18 18 6 6 18 18 — 38PEA (parts by mass) — — — — — — — 18 — Additive (parts by mass) 2 2 2 44 2 2 2 2 Glass transition temp. (° C.) 100 100 100 103 103 75 75 76 95Crystallization temp. (° C.) 170 170 170 166 166 132 132 134 175 Meltingpoint (°C.) 261 261 261 261 261 261 261 261 260 Molding conditionsOutside heater temp. (°C.) 700 650 500 700 600 500 450 500 700 Insideheater temp. (°C.) 500 600 450 500 550 350 450 350 500 Preformouter-wall 165 160 140 164 161 130 125 130 165 surface temp. (° C.)Preform inner-wall 152 161 139 152 161 115 125 115 151 surface temp. (°C.) Crystallinity (%) of belt on 47 45 40 45 45 39 38 40 25outer-peripheral surface side Crystallinity (%) of belt on 42 45 38 4045 34 38 35 20 inner-peripheral surface side

TABLE 8 Comparative Example: 1 2 3 4 5 6 7 8 9 Volume resistivity (Ω ·cm) 2 × 10¹¹ 1 × 10¹¹ 1 × 10¹¹ 3 × 10¹¹ 3 × 10¹¹ 3 × 10¹¹ 8 × 10¹⁰ 1 ×10¹¹ 4 × 10¹⁰ Average aspect ratio of 15 15 16 18 18 15 16 16 7discontinuous phases Average height of 160 125 135 140 130 130 125 150130 permanent curl Image evaluation B B B B B B B B B

Cross sections in the peripheral directions of the conductive beltsaccording to Examples 1 to 9 and Comparative Examples 1 to 9 wereobserved on a field emission scanning microscope (FE-SEM) XL30 (tradename; manufactured by FEI Technology Co.) at magnifications of 5,000times. As the result, the conductive belts according to Examples 1 to 9were, compared with the conductive belts according to ComparativeExamples 1 to 9, seen to have vastly much less come to crack at theinterfaces between the continuous phase and the discontinuous phasespresent in the vicinity of their outer peripheral surfaces. Also, aboutthe average height of permanent curl, the conductive belts according toExamples achieved its reduction by 45 μm at the minimum, compared withthat of the conductive belts according to Comparative Examples. Such adifference in height of permanent curl in intermediate transfer beltshas a great influence on the transfer precision of toner images duringtheir primary transfer in the formation of electrophotographic images,and furthermore the grade of the electrophotographic images.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2010-042730, filed Feb. 26, 2010, which is hereby incorporated byreference herein in its entirety.

1. A cylindrical conductive belt for electrophotography comprising: acontinuous phase which comprises a thermoplastic polyester resin; anddiscontinuous phases each of which comprises any one or both selectedfrom a polyether-ester amide and a polyether amide; said discontinuousphases being present in such way as to extend in the peripheraldirection of said cylindrical conductive belt; wherein a crystallinityof an outer-peripheral surface side of said cylindrical conductive beltis lower than that of an inner-peripheral surface side of saidcylindrical conductive belt.
 2. The conductive belt according to claim1, wherein the thermoplastic polyester resin contains any one or bothselected from a polyalkylene terephthalate and a polyalkylenenaphthalate.
 3. The conductive belt according to claim 2, wherein thepolyalkylene terephthalate and the polyalkylene naphthalate arepolyethylene terephthalate and polyethylene naphthalate, respectively.4. An electrophotographic apparatus comprising the conductive beltaccording to claim 1 as an intermediate transfer belt.